test: migrate 700_e2e rows to corpus fixtures; retire the carrier

136 rows migrated, 0 already owned, 3 wwstage-failing rows held out.

test/wcc/data/r700_bang_alias_param/case.ww

@@ -0,0 +1,17 @@
+//ww:run-exit 7
+// Migrated from 700_e2e row 56.
+package main;
+type invalid  = !i32;
+type overflow = !void;
+type error    = !(invalid | overflow);
+fn errcode(e: error) i32 = {
+  match (e) {
+    case let v: invalid  => return v: i32;
+    case let v: overflow => return 99;
+  };
+  return 0;
+};
+fn main() i32 = {
+  let e: error = 7: invalid;
+  return errcode(e);
+};